Objective: Patients with chronic obstructive pulmonary disease (COPD) and coronary artery disease (CAD) are associated with exercise intolerance. Whether exercise intolerance and reduced mechanical efficiency are due to inactivity alone or to disease related muscular abnormalities is not clear. The aim was to find out whether two patient groups with different limitations for exercise had the same mechanical inefficiency.
Design: CAD and COPD patients were compared to a healthy age matched reference group in walking and cycling mechanical efficiency.
Results: Both patient groups showed a similar mechanical inefficiency when walking (COPD 16.9 +/- 6.4%, CAD 19.2 +/- 4.1%) compared to healthy controls (24.7 +/- 6.4%). No differences were found when bicycling. VO2peak (mL x kg(-1) x min-1) was significantly reduced in both patient groups compared to the healthy controls (COPD = 23.1+/- 5.3, CAD = 27.9 +/- 3.6, Healthy controls = 36.2 +/- 7.1).
Conclusion: Both COPD and CAD patients show mechanical inefficiencies when walking compared to healthy controls. Inactivity is a common feature between the two patient groups, whereas the exercise limitations are quite different. These findings indicate that the mechanical inefficiency might primarily be caused by inactivity.